We have two Varian CP-3800 GC units. In the analysis* with TSD (GC1) and TSD or FID (GC2) both chromatographs show a progressive reduction of signal in the detection of nicotine during the day (for example, using TSD in a day the initial ABC is 1000 in the morning and the final ABC is 800-900 in the afternoon). Because both chromatographs are showing the same problem and share the main gas supply lines, we verify and there are no gas leaks.*Using very similar methods: same capillary column type, program temperature, standard solution (fresh or old), solvent, etc.
Does anyone know why this is happening? Reply to Luz Soriano RE: Varian - CP-3800